1. Field of the Invention
The present invention relates to an electrophotographic member for use in an electrophotographic apparatus, and a process cartridge and an electrophotographic apparatus having the electrophotographic member.
2. Description of the Related Art
In an electrophotographic apparatus (for example, a copier, a facsimile, and a printer using an electrophotographic system), an electrophotographic photosensitive member (hereinafter, also referred to as “photosensitive member”) is charged by a charging unit and exposed by laser or the like, and as a result, an electrostatic latent image is formed on the photosensitive member. Then, a toner in a developing container is applied on a developer carrying member by a toner supplying roller and a toner regulating member. The electrostatic latent image on the photosensitive member is developed on a contact portion between the photosensitive member and the developer carrying member, or in close proximity of the contact portion, by the toner conveyed to a developing area by the developer carrying member. Thereafter, the toner on the photosensitive member is transferred by a transfer unit to recording paper and fixed by heat and pressure, and the toner remaining on the photosensitive member is removed by a cleaning blade.
An elastic roller having an electric resistance of 103 to 1010 Ω·cm is generally used for the developer carrying member. In addition, in view of needs for the developer carrying member to have more increased durability and for an electrophotographic image to have a more increased image quality, a developer carrying member in which a surface layer is provided on the surface of an elastic layer has been increasingly used.
Herein, a polyurethane excellent in wear resistance and charge-imparting property to a toner is used for the surface layer in the developer carrying member. In particular, a surface layer using a urethane resin having low hardness has been used in recent years in order that products may have a longer lifetime.
Japanese Patent No. 4812115 discloses a method for suppressing the fusion (filming) of a toner on the surface of a roller by using, for the outermost layer, a silicone graft modified urethane having a defined elastic modulus and the like. In addition, Japanese Patent No. 3572905 discloses a method for suppressing the fusion (filming) of a toner on the surface of a roller by using at least one of polycarbonate urethane, an acrylic-vinyl acetate copolymer, and acrylic-modified urethane.
Furthermore, Japanese Patent No. 4042755 discloses a developer carrying member using a polyurethane surface layer for which a polyether-based polyol having a particular molecular weight, a diisocyanate, and an aromatic difunctional chain extender are used in order to enhance toner adhesion resistance to a toner having a low melting point.